docs: def GetMaximum(self, expression, cut=None):
          """
          TODO: we need a better way of determining the maximum value of an
          expression.
          """
          if cut:
              self.Draw(expression, cut, 'goff')
          else:
              self.Draw(expression, '', 'goff')
          vals = self.GetV1()
          n = self.GetSelectedRows()
          vals = [vals[i] for i in range(min(n, 10000))]
          return max(vals)